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GWAS of Parkinson's Disease
Introduction: Genomics is defined as: a discipline ingenetics that applies recombinant DNA, DNA sequencing methods, and bioinformatics to sequence, assemble, and analyze the function and structure of genomes (the complete set of DNA within a single cell of an organism) 2. Within the field of genomics, there is a specific type of study called a genome-wide association study, or a GWAS. Genome-wide association studies are examinations of the common genetic variants in different organisms to see if a specific variant is associated with a trait 2. In other words, they are studies that look at the differences within the DNA sequences of different organisms (of the same species) and determine which, if any, variations within the DNA are causing a specific trait and/or disease. These studies are very important in figuring out the underlying genetic causes of diseases and are a step in the direction of possible cures. Parkinson’s Disease: Parkinson’s disease is a progressive disorder of the nervous system that affects one’s movement 3. The disease is very slow to progress and starts with a hand tremor, which can develop into stiffness and slowing of movement. It affects the nerve cells within the brain that produce dopamine. Other symptoms of Parkinson’s may include muscle rigidity and changes in speech and gait 4. Although there is no current cure for the disease, there are some treatments that can help to relieve symptoms. GWAS of Parkinson’s: A GWAS was performed focusing on Parkinson’s disease, and the results were very important. A study including 1,713 Caucasian patients with Parkinson’s disease and 3,978 controls was carried out to expose genomic variations between the two experimental populations. This study revealed two important areas within the DNA of the patients that had strong associations with Parkinson’s. Variations within the α-synuclein gene (SNCA) (rs2736990) and the MAPT locus (rs393152) were both areas of high significance 1. Within these specific regions of DNA, variations from the controls were observed within patients with Parkinson’s. This experiment was taken one step further and compared to Asian Parkinson’s disease cases and an association at SNCA was confirmed as a major risk factor across populations. When collaborating data, another locus (LRRK2) was proven to have significance in determining a person’s susceptibility to Parkinson’s disease 1. In summation, patients with genetic variations from the control group at the SNCA and/or MAPT locus were the ones who had Parkinson's disease. This experiment, and others like it, is essential for determining the underlying genomic causes of many various diseases. Conclusion: Genome-Wide Association Studies are very important for linking diseases to their genetic causes, if genetics play a role with that particular disease. By comparing the genomes of people who have a disease to the genomes of people who do not have a disease, variations within the DNA of each group can be highlighted. Once it is known what parts of the DNA are associated with the disease state, a treatment or therapy can be created to alleviate patients of the disease (ideally). Within the study covered above, the data demonstrates an unequivocal role for common genetic variability in the etiology of typical Parkinson’s disease and suggests population specific genetic heterogeneity for the disease 1. Resources: 1. GWAS Reveals Genetic Risk Underlying Parkinson’s Disease on PubMed PMCID: PMC2787725 2. Genomics and GWAS by Wikipedia.org 3. Parkinson’s Disease: Disease and Conditions by The Mayo Clinic 4. Parkinson’s Disease Health Center by WebMD